The Core zone, commonly
also known as the Omineca Geanticline, merges at its northern end
with the Yukon-Tanana Platform, a structural unit which to the west of
the Intermontane zone can be traced southwards into the Coast Crystalline
complex.

The relative plate tectonic
evolution of these three tectonic elements remains one of the major 'unknowns'
of Cordilleran and Canadian geology.

In terms of the concept
of 'suspect terranes', the Cordillera is now recognized as
an accretionary complex composed, from east to west, of the following native
and accreted terranes:

The Pericratonic terranes
contain volcanic and continental derived sedimentary rocks laid down
during early Phanerzoic rifting of the western margin of North America
They have a late Proterozoic to Paleozoic history of deformation and plutonism. The Slide Mountain (Miss. to
Permian), and Cache Creek/Bridge River (Mississipian to Upper Triassic)
terranes represent Paleozoic/Mesozoic oceans, whereas the Quesnellia
(Upper Triassic to Middle Jurassic), Stikinia (Devonian to Middle Jurassic),
Cadwallader (Upper Triassic to Mid Cretaceous), and Gravina (Jurassic to
Cretaceous) terranes are remnants of arc systems accreted to North
America. The Alexander (Precambrian to Lower Triassic) and Wrangellia
(Permian to Lower Jurassic) terranes were amalgamated during the
Middle Jurassic but were not accreted to North America until the
Cretaceous. The exact timing and mechanism of accretion, and the original
location of the terranes, remains a subject of debate.

The continental margin miogeoclinal rocks (Ketchika basin) of the Cordilleran System

Ferri, Filippo, Rees, Chris,
Nelson, JoAnne, Legun, Andrew, Orchard, M-J, Norford, B-S, Fritz, W-H,
Mortensen, J.K, Gabites, J-E, 1999. Geology and mineral deposits of the
northern Kechika Trough between Gataga River and the 60th parallel. Bulletin
- British Columbia Ministry of Energy and Mines, Energy and Minerals Division,
Geological Survey Branch. 107, 122 p., 2 sheets. Abstract
- The Kechika Trough represents a Lower Paleozoic
basin developed between the MacDonald Platform to the east and the
Cassiar Platform to the west. This basin was well established by Late Cambrian
time and ceased to be a depositional entity at the beginning of the Late
Devonian. Mapping along the western part of the trough, between the Gataga
River and the 60th parallel, encountered layered rocks of Proterozoic to
Cenozoic age. These include:
Late Proterozoic siliciclastics,
carbonates and volcanics; siliciclastics and carbonates of Cambrian
age; Late Cambrian to Early Ordovician calcareous
argillites and argillites of the Kechika Group;
slate,
siltstone and minor limestone of the Middle Ordovician to Middle Devonian
Road
River Group;
Late Devonian to Early Mississippian
argillite, chert and minor limestone of the Earn
Group; chert, tentatively assigned to the Mississippian
to Permian Mount Christie Formation;
conglomerate and sandstone of possible Tertiary age; and Tertiary to Quaternary
mafic volcanics assigned to the Tuya Formation. Intrusive rocks represent
a very minor component of the map area and consist of Early
Paleozoic sills and dikes of gabbroic composition, feldspar porphyry
dikes of Cretaceous or Tertiary age and small Early Cretaceous stocks,
dikes and sills of broadly granitic composition. Periodic extensional tectonism
during the Paleozoic, which led to the formation and subsequent modification
of the Kechika Trough, was followed by intense, easterly directed, compressional
tectonics and associated metamorphism of Mesozoic age, resulting in the
present structural configuration. Rocks of the trough belong to the Rocky
Mountain structural province and structures aredominated by easterly verging folds and thrusts. Thrust
faulting predominates in the southern part of the map area where lithologies
are dominated by thick, competent Cambrian carbonate and quartzite units.
Their disappearance to the north results in a structural style dominated
by folding and penetrative cleavage. Sedimentary exhalative mineralization
(sedex) represents the most important mineral deposit type found within
the Kechika Trough, ranking it, and the more northerly Selwyn Basin, as
one
of the most important metallotects of the Canadian Cordillera.
These stratiform Zn-Pb-Ag-Ba deposits are found at several stratigraphic
levels: Cambrian, Middle Ordovician, Lower Silurian and Upper Devonian.
Upper
Devonian deposits are by far the most numerous and economically important
within the map area, and throughout the Kechika and Selwyn basins. The
large Cambrian and Early Silurian deposits found in the Anvil and Howards
Pass districts, respectively, highlight the potential that all these horizons
have for hosting economically significant sedex deposits. Tungsten-molybdenum
porphyry/skarn mineralization related to Early Cretaceous intrusions is
the next most important mineral deposit type. Minor lead, zinc and copper-bearing
veins are scattered throughout the map area.

Smith, M. Gehrels, G., 1994, Detrital
zircon geochronology and the provenance of the Harmony and Valmy formations,
Robert Mountains allochthon, Nevada: BGSA, 106, 7, 968-979. Abstract- Valmy zircons - 2 of
1050, 4 of 1830-1845, 5 of 1910-1960, 2 of 2270-2340, 8 of 2650-2750, 1
of 2900 and discordant ages 1 of 2070 1 of 3240; derivation from the North,
Slave Craton and Medicine Hat province and central/northern Alberta; Valmy
is Ordovician volcanic bearing equivalent of the Eurekea Quartzite of the
shelf miogeocline; Harmony Fm is Upper Cambrian and immature, zircons -
9 of 695-710, 12 of 1015-1225, 2 of 1330, 1 of 1745, 1 of 1915, 1 of 2570;
the c 700 and c 1100 have no western North American basement source; five
foliated intrusive bodies spatially associated primarily with the Windermere
Supergroup and Yukon-Tanana terrane , as well as one extrusive unit Mount
Harper rhyolite in the Ogilvie Mountains 751+26-18, yield ages in the 670-750
range. Two 680 orthgneiss bodies occur in the Seward Peninsula;evidence
for Grenville age basement includes clasts and xenoliths entrained in two
diatremes and a monazite age from a breccia pipe; Pahrump sills of Death
Valley are 1069 1087 and sills in the Apache quartzite of Arizona are 1150
Ma.

What is the Monashee?

James L. Crowley, 2001. U-Pb
geochronologic constraints on Paleoproterozoic tectonism in the Monashee
complex, Canadian Cordillera: Elucidating an overprinted geologic
history Canada.Geological Society of America Bulletin: Vol. 111, No. 4,
pp. 560–577. Abstract: The effects of Paleoproterozoic
tectonism are best preserved in deep structural levels of the complex,
where overprinting related to high-grade Cordilleran (early Tertiary) metamorphism
and deformation was incomplete. Determination of precise crystallization
ages is hindered by the U-Pb age discordance in the zircon, monazite, and
titanite; the discordance is attributed to inherited Pb in some of the
grains and to Pb loss, overgrowth, and recrystallization that ccurred during
one or more thermal overprints. Igneous crystallization ages are interpreted
from the upper intercepts of linear arrays that are defined by three
or more analyses. Varying degrees of confidence are attributed to the ages
based on the probability of inheritance. Large bodies of augen orthogneiss
and granodioritic orthogneiss yield precise igneous crystallization ages
of 2077 ± 2 and 1862 ± 1 Ma, respectively. Crystallization
ages of about 2.27 and 2.10 Ga are interpreted with less certainty from
dioritic orthogneiss and granitic orthogneiss, respectively. Deformation
associated with a migmatitic gneissosity occurred after ntrusion
of the 2077 ± 2 Ma augen gneiss, the youngest dated rock that contains
the fabric, and before intrusion of a 1848 ± 3 Ma granite, the oldest
confidently dated rock that postdates the fabric. Postdeformational pegmatite
dikes are dated as 1845 ± 3 nd 1836 ± 2 Ma. Metamorphism
is interpreted as occurring during monazite growth at 2060 ± 1 Ma
in pelitic schist and during titanite growth at ca. 1.85 Ga in amphibolitic
gneiss. The gneisses are basement to an unconformably
overlying cover sequence, the lower part of which was deposited
prior to intrusion of a 1852 ± 4 Ma pegmatite.

Roback, R.C., Sevigny, J.H., and Walker, N.W., 1994.
Tectonic setting of the Slide Mountain terrane, southern British Columbia.
Tectonics, 13, 5, 1242-1258. Abstract - SMT consists of fine
grained quartzose clastic rocks, limestone and lesser amounts of conglomerate
and volcanic rocks of the Carboniferous McHardy assemblage conformably
overlain by the Permian Kaslo Group ultramafic, volcanic and sedimentary
rocks. Kalso volcanics are MORB. McHardy conglomerates
contain clasts of Silurian granitoid rocks,
and detrital zircons in the McHardy are 1.7 to 3.1 Ga, similar to ages
of zircons in the Kootenay and miogeoclinal sediments. The SMT is unconformably
overlain by Late Triassic fined grained sedimentary rocks of the Slocan
Group of the Quesnellia terrane (Monger and Berg, 1987). The Slide
Mountain may therefore be in part a 'native' foreland basin assemblage,
rather than an exotic section of oceanic crust.

Henderson-Charles-M,
1998. Tectonic control and biotic change at the Permian-Triassic (P-T)
and Dienerian-Smithian (D-S) sequence boundaries, Western Canada.
Abstracts with Programs - Geological Society of America. 30, 7, p.
152. Abstract - Permian and Lower Triassic
strata in western Canada are difficult to correlate because of major thickness
and lithofacies variations and the scarcity of index fossils. However,
sequence biostratigraphic analysis using conodonts, has resulted
in the development of a complex tectono-stratigraphic history for
the cratonic margin of northwestern Pangea. At least five third-order sequences
are recognized for the Permian and Lower Triassic of western Canada. A
thin Upper Asselian/Lower Sakmarian sequence, is sporadically distributed
as a result of sub-Permian tectonic uplift and buckling on the craton margin.
The remaining two Permian sequences (Artinskian-Lower Kungurian and Roadian-Wordian)
are more widespread and are characterized by condensed sedimentation and
decreasing biotic diversity that point to a protracted extinction interval.
A low diversity Upper Permian fauna is dominated by siliceous sponges and
associated with dropstones, suggesting that climatic cooling as well as
the subsequent regression were important contributing factors to the P-T
extinction locally. Truncation of various Upper Paleozoic units and localized
distribution of latest Permian and earliest Triassic strata indicates another
major
tectonic uplift and buckling event that correlates with the Sonoman Orogeny,
immediately before the Permian-Triassic biostratigraphic boundary.
A relatively thick latest Changhsingian to Dienerian sequence includes
a very low diversity fauna and few ichnotaxa. The D-S sequence boundary
has a comparable tectonic signature that isolated overlying biotic accumulations,
forming important reservoir units in the region. Evidence supports
emplacement of allochthonous terranes (Slide Mt.)
onto pericratonic terranes (Kootenay) and
imbrication
of Upper Permian rocks beginning in pre-Late Triassic time. Therefore,
it is probable that tectonic stress buildup and release events associated
with major plate reorganizations or interaction between the craton margin
and pericratonic and allochthonous terranes controlled these northwestern
Pangea sequence boundaries and influenced biotic extinction and migration
patterns.

Armstrong, R.L. and Ghosh, D.K. 1990.
Westward movement of the 87Sr/86Sr=0.704 line in southern B.C. from Triassic
to Eocene time: monitoring the tectonic overlap of accreted terranes on
North America. GAC Abst. w. Prog., Vancouver, pA4. Abstract - Prior
to late Triassic and early Jurassic all magmatic rocks of Quesnellia had
Sr/Sr below .704, therefore oceanic.By
middle Jurassic (accretion of Stikinia - Western Paleozoic and Triassic
of the Klamaths) the .704 line had shifted 200 km westward of the leading
edge of Quesnellia to just west of the Okanagan Valley. In the east
Middle
Jurassic plutons stitch the fault separating Quesnellia from North America;
suturing took place in late Early to early Middle Jurassic. By mid-Cretaceous
(accretion of Wrangellia) the .704 line had moved only a further 25km westwards,
but by Eocene time ( it had moved 75 km west of the Okanagan valley. During
mid-Cret to Eocene seds of the fold and thrust belt in eastern B.C. moved
200 km eastwards. At depth this movement must have been partitioned
into crustal thickening to accommodate 125 km of shortening, and 75 km
of additional overriding of N.America by Quesnellia. The amount of
tectonic overlap observed today must be reduced by 75 km to account for
extension. Seds of the fold and thrust belt were
deposited on the basement which presently underlies Quesnellia.

Smith, A.D. and Lambert, R.S., 1995.
Nd, Sr, Pb isotopic evidence for contrasting origins of late Paleozoic
volcanic rocks from the Slide Mountain and Cache Creek terranes, south-central
British Columbia. CJES, 32, 447-459.Map
of sample areas in the Fennel allochton (Slide Mountain) and southern Cache
Creek terranes - cord2smith1.jpgComment - Slide Mountain Fennell
Fm Late Pennsylvanian basalts resemble MORB but have kaersutite or augite
dominated mineralogies; EpND300 = +7.7 to +10.2. Pb isotope values
favour a marginal basin rathern than a back arc. Cache Creek of the Bonaparte
subterrane (middle Mississippian?) are within-plate. EpNd340 = +4.2-+5.6,
and lead shows a transition towards DUPAL signatures. Baslatic andesite
and andesitic tuffs, also found in the Bonaparte subterrane, are tentatively
correlated with Late Triassic to Early Jurassic low-K tholeiite of the
Nicola Group of Quesnellia.

Erdmer, P. Thompson, R. I., and
Daughtry, K. L., 1999. Pericratonic Paleozoic succession in Vernon and
Ashcroft map areas, British Columbia. In: Cordillera and Pacific margin/
Interior Plains and Arctic Canada. Current Research - Geological Survey
of Canada. 205-213. Comment:
Ductilely deformed and metamorphosed pericratonic rocks of inferred Early
Paleozoic age overlie the Neoproterozoic-Eocambrian Silver
Creek schist in the Vernon map area along an apparent stratigraphic contact.
Permian
(Harper Ranch Group) and Triassic (Nicola Group and Slocan Formation) strata
overlie the pericratonic succession along an unconformable depositional
contact. The pericratonic succession, long recognized to include
amphibolitic schist, marble, and quartzite, includes in addition
to these a distinctive metaconglomerate, and forms a robust regional
marker. The tripartite regional stratigraphy and its inferred Proterozoic
or older depositional basement cross the Okanagan Valley without apparent
offset, and persist for at least 100 km westward, as far as the Nicola
horst. The pericratonic succession underlies rocks presently assigned
to the Quesnellia terrane at this latitude.

Eocambrian granite clasts in southern British Columbia
shed light on Cordilleran hinterland crust Philippe Erdmer, Larry
Heaman, Robert A. Creaser, Robert I. Thompson, and Ken L. Daughtry
Can. J. Earth Sci./Rev. Can. Sci. Terre 38(7): 1007-1016
The Spa Creek assemblage is a distinctive thin pericratonic succession
that crosses the Okanagan Valley in the hinterland of the southern Cordilleran
Orogen in Canada. The succession was ductilely deformed and metamorphosed
before deposition of overlying Triassic dark metaclastic strata. A metaconglomerate
within the succession, locally composed of more than 90% biotite
granite clasts, yielded five fractions of euhedral zircon that define a
precise U–Pb upper intercept of 555.6 ± 2.5 Ma, inferred to be the
age of a nearby pluton. Other clasts in the metaconglomerate are generally
more abundant, consisting of quartzite, amphibole schist, chlorite schist,
sericite schist, biotite schist, and quartz–feldspar porphyry. They are
likely host rocks of the pluton and, if so, are Late Proterozoic or older.
The granite is interpreted as a terminal product of the Eocambrian rifting
that preceded Paleozoic miogeoclinal sedimentation farther inboard. The
continuity of pericratonic rocks west of the miogeocline and the
occurrence of Proterozoic cratonic rocks at the surface west of the Okanagan
Valley show that the ancient continental margin extends into a region where
most of the crustal lithosphere was until now thought to consist of accreted
Phanerozoic arc and accretionary complexes.Western
extent of the eastern Cordillera beneath Quesnellia - cordspacreek.jpg

Nature of the basement to Quesnel Terrane near Christina
Lake, southeastern British Columbia S.L. Acton, P.S. Simony, and L.M. Heaman,
Can. J. Earth Sci., 39(1), p. 65-78
The character of the Paleozoic basement of Quesnel Terrane and the position
of the terrane accretion surface that separates Quesnel and Kootenay terranes
from rocks of the ancient North American margin are subjects of debate.
To address these problems, detailed mapping and U–Pb geochronologic
studies were carried out in the Christina Lake area to define the relationship
of the Mollie Creek assemblage, Josh Creek diorite, and Fife diorite to
similar lithologies in the Greenwood – Grand Forks and Rossland regions,
and to place limits on the ages of regional deformation and local position
of the terrane accretion surface. Deformed metasedimentary rocks of the
Mollie Creek assemblage may correlate with sedimentary rocks of the Pennsylvanian
to Early Triassic Mount Roberts Formation in the Rossland area. The
Mollie Creek assemblage is intruded by the foliated Late Triassic
Josh Creek diorite. The Josh Creek diorite and Mollie Creek assemblage
have been deformed together as a result of phase two deformation, following
the intrusion of the Josh Creek diorite in the Late Triassic and prior
to the intrusion of the Fife diorite and deposition of the overlying
Rossland Group in the Early Jurassic. Based on relative age, structural
position, and lithological similarities to other units within Quesnel
Terrane, the Mollie Creek assemblage, Josh Creek diorite, and Fife diorite
are a part of Quesnel Terrane and lie above the terrane accretion surface
in theChristina Lake area. Therefore, Quesnel Terrane does not unconformably
overlie basement rocks of known North American affinity in this region.Relative
disposition allochthonous and pericratonic terranes according to
Acton et al. - cordchris1.jpgDistribution
of North American Precambrian crust within the Quesnel Terrane of the Southern
Canadian Cordillera - cordchris2.jpgGeological
section across the Quesnel Terrane showing the horst structure of the Grand
Forks - Kettle River Complex - cordchris3.jpg

What
do the isotopic characteristics of Cordilleran terranes tell us about their
origin?

Patchett, P. J. and Gehrels, G. E, 1998. Continental influence of Canadian
Cordilleran terranes from Nd isotopic study, and significance for
crustal growth processes. Journal of Geology. 106, 3, 269-280. Comment
- Nd isotopic data are presented for rocks of the terrane assembly that
lies inboard of the Stikine terrane in the Canadian Cordillera of
British Columbia and Yukon. These are, from most inboard outward:
Cassiar,
Kootenay, Slide Mountain, Quesnel, and Cache Creek terranes. They
are regarded as documenting a transition from terranes whose evolution
was closely tied to that of the North American continental margin
out to far-traveled oceanic terranes. The results emphasize sedimentary
rocks as indicators of tectonic position of the crustal fragments.
Sedimentary
rocks of the Cassiar and Kootenay
terranes show a strong connection to miogeoclinal sediment sources.
Argillites of Pennsylvanian-Permian age from a paleontologically
controlled section in the Slide Mountain terrane
are also consistent with sediment sources in the North American miogeocline.
Igneous
rocks of the Slide Mountain, Quesnel, and
Cache Creek terranesshow
juvenile oceanic or arc origins based on
epsilonNd
values between +3 and +10, and are essentially identical with published
results.
Cache Creek and
Quesnel terranes also contain
sediments
with positive epsilonNd values, suggesting a juvenile, ultimately
volcanogenic, origin. Both terranes, however, also contain some
Triassic
and apparently Pennsylvanian-Permian sedimentary rocks with negative epsilonNd
values between -5 and -7, like those of Devonian to Jurassic sedimentary
rocks of the North American miogeocline.
Possible explanations include proximity to sources of North American terrigenous
sediment, expected in Triassic time, or very far-traveled fine-grained
sediment in the form of hemipelagic clay or eolian dust for older samples.
The addition of a continental sedimentary component to wide areas of the
Cordillera represents an important point of comparison to Proterozoic orogens,
where this component affected the isotopic signatures, but usually cannot
be separately identified due to intense reprocessing during orogenesis.

Cui, Y.
and Russell, J.K. 1995. Nd-Sr-Pb isotopic studies of the southern Coast
Plutonic Complex, Southwestern British Columbia. BGSA, 107, 2, 127-138. Abstract
- Plutonic and volcanic rocks have EpNd values of +4.2 to +8.9. There
are no significant variations in Nd or Sr isotopic composition with rock
type or age. Many intrusions have isotopic compositions and TDM ages consistent
with the combined effects of melting of mantle and mixing with subordinate
istopically juvenile terranes, e.g. Wrangellia.

Johannson-G.G.; Smith-P.L.; Gordey-S.P.,
1997. Early Jurassic evolution of the northern Stikinian Arc: evidence
from the Laberge Group, northwestern British Columbia. Canadian-Journal-of-Earth-Sciences.
34, 7, 1030-1057. Abstract: This study
resolves fundamental questions concerning the age, provenance, and depositional
history of Laberge Group strata in the Whitehorse Trough. The Jurassic
Inklin Formation straddles the Stikine and Cache Creek terranes along much
of the length of the Whitehorse Trough. Ammonite biochronology indicates
an age range of early Sinemurian to late Pliensbachian
and provides the temporal framework for interpreting basin history. Strong
temporal trends in both paleocurrent patterns and sandstone-conglomerate
petrofacies allow definition of three discrete phases in basin-fill history.
Stable tectonics characterized by relative volcanic quiescence and low
sedimentation rates prevailed during the Sinemurian.
Sinemurian sandstone-conglomerate petrofacies record a transitional-arc
provenance derived from erosion of the Upper Triassic
volcanic pile, flanking coastal sediments, and arc
roots of Stikinia to the southwest. During the early
Pliensbachian, arc dissection was interrupted by a major magmatic
episode with widespread rejuvenated volcanism that caused a strong provenance
shift to volcanigenic sources, indicating derivation from a largely undissected
Stikinian arc. Southwest-derived, northerly longitudinal paleoflow during
the Sinemurian changed to opposed bidirectional
radial or transverse paleoflow systems in the early
Pliensbachian. Cannibalism of broadly coeval basinal strata and/or
reflected sediment gravity flows were the result of episodic growth of
a
mobile outer forearc rise, initiating southwest-directed
paleoflow systems during the early Pliensbachian
and
the possible development of a ridged forearc phase. U-Pb dates of 186.6
-1/+-.5 and 186 +/- 1 Ma from a granite clast and tuff unit, respectively,
of the Kunae Zone (early late Pliensbachian)
and sandstone-conglomerate petrofacies indicate a late
Pliensbachian depositional regime dominated by tectonic controls.
The influx of granitic detritus indicates a rapid transition to a
fully dissected arc provenance, where accelerated uplift of segments
of the arc massif, accompanied by intra-arc strike-slip faulting, resulted
in rapid arc dissection and unroofing of comagmatic Pliensbachian
plutons.

Orchard-M-J; Struik-L-C; Taylor-H; Quat-M, 1999. Carboniferous-Triassic
conodont biostratigraphy, Nechako NATMAP Project area, central British
Columbia. In: Cordillera and Pacific margin/ Interior Plains and
Arctic Canada--Cordillere et marge du Pacifique/ Plaines interieures et regions arctiques du Canada. Current
Research - Geological Survey of Canada. 97-108. Abstract: Fifty-seven new conodont
collections from the Nechako NATMAP area contribute to a conodont biostratigraphic
framework for the region. Most collections are from the Pope unit of the
Cache
Creek complex and are early Late Carboniferous
(Bashkirian-Moscovian) to Middle Permian (Wordian). The most extensive
carbonate
buildup is Bashkirian-Moscovian, whereas latest Carboniferous to Permian
limestone is much less common and Middle Permian
buildups are known only in the north. The Sowchea
clastic-volcanic
unit is Late Permian to Late Triassic (Norian);
it includes unique records of (?)Changshingian, Griesbachian, and Smithian
fauna, and the first records of Middle Triassic Tethyan
Gladigondolella in Canada. At two widely separated localities, breccia
containing mixed conodont faunas show that Paleozoic and Triassic strata
were reworked during or after the Late Triassic.
Late
Triassic conodonts are also reported from the Tezzeron unit and adjacent
Takla
Group of the Quesnellia terrane.

The 'exotic' nature of Stikinia and Wrangellia

Aberhan, M. 1999.Terrane history of
the Canadian Cordillera: Estimating amounts of latitudinal displacement
and rotation of Wrangellia and Stikinia.Geological-Magazine. 136, 5,
481-492. Comment: The Canadian Cordillera
is largely a mosaic of terranes that are allochthonous relative to the
autochthonous North American craton. Palaeobiogeographic data on pectinoid
bivalves from various cratonal areas and from two western Canadian terranes,
Wrangellia and Stikinia, are used to estimate the amounts of latitudinal
displacement and rotation of these terranes that took place during and
after Early Jurassic times. Distributional patterns of various species
of the distinctive, very common bivalve Weyla, and a comparison of the
positions of biogeographic boundaries between high-palaeolatitude, mixed
and low-palaeolatitude faunas on the terranes and on the craton indicate
that Wrangellia was displaced northward relative
to the craton by at least several hundred and possibly more than
1000 km since Sinemurian and Pliensbachian times. For
Stikinia such estimates are even higher and exceed 1000 km. Biogeographic
patterns also suggest that Wrangellia experienced at best minor rotation
since Sinemurian times, while rotation from a more or less east-west alignment
to its present northwest-southeast position seems possible for Stikinia
prior to the Pliensbachian. Palaeomagnetic interpretations,
suggesting that during Sinemurian and Pliensbachian times Wrangellia and
Stikinia were in much the same latitudinal position relative to the craton
as they are now, are in sharp contrast to the results from faunal data.
The presence of warm oceanic surface currents, oceanographic effects of
elongated barriers, climatic change and differential latitudinal displacements
due to rotation appear to be insufficient explanations for the discrepancy
between the interpretation of palaeomagnetic and faunal evidence.

Aberhan, M, 1998. Paleobiogeographic
patterns of pectinoid bivalves and the early Jurassic tectonic evolution
of western Canadian terranes. Palaios. ; 13(2): 129-148. Asbtract: Utilizing new data
from western Canada, the biogeography of Early Jurassic pectinoid bivalves
along the eastern paleo-Pacific margin has been analyzed qualitatively
and quantitatively. The studied areas range from the Andean Basin in the
southern hemisphere to the Sverdrup Basin of Arctic Canada and include
major allochthonous terranes of western Canada. While the Andean Basin
exhibits a mixed bivalve fauna of austral, bipolar, and low latitude-East
Pacific forms, pectinoid bivalves from the Canadian craton are characterized
by a high percentage of boreal and bipolar taxa. The western Canadian allochthonous
terranes Wrangellia and Stikinia show a mixed influence of low latitude-East
Pacific and boreal/bipolar forms until Pliensbachian times. During the
Toarcian/Early Aalenian, taxa typical of low latitudes disappeared. This
pattern of a latitudinally differentiated Early Jurassic bivalve fauna,
which apparently is climatically controlled, seriously undermines
the hypothesis of a uniform West American bivalve province. Based on diversity
gradients, similarity coefficients, cluster analyses, and distributional
patterns of characteristic taxa, biogeographic data have been used to constrain
the latitudinal positions of Wrangellia and Stikinia through time. During
the three analyzed time intervals (Hettangian/Sinemurian, Pliensbachian,
and Toarcian/Early Aalenian), both terranes were in the northern hemisphere
and in the eastern paleo-Pacific. During all of the Early Jurassic, Wrangellia
and Stikinia were close together and were moving northward. Paleolatitudes
corresponding to those of the Western Canada Sedimentary Basin in Alberta
were not reached before Toarcian times. By the end of the Early Jurassic,
both terranes were in much the same latitudinal position relative to the
craton as they are now. Consistent with biogeographic
patterns are Early Jurassic latitudinal displacements of approximately
1300 km.

Harris-M.J.;
Symons-D.T.A.; Blackburn-W.H.; Hart-C.J.R., 1997. Paleomagnetic and geobarometric
study of the mid-Cretaceous Whitehorse Pluton, Yukon Territory. Canadian-Journal-of-Earth-Sciences.
34, 10, 1379-1391. Abstract:
This is the first of several Lithoprobe paleomagnetic studies underway
to examine geotectonic motions in the northern Canadian Cordillera. Except
for one controversial study, estimates for terranes underlying the
Intermontane Belt in the Yukon have been extrapolated from studies in Alaska,
southern British Columbia, and the northwestern United States. The
Whitehorse Pluton is a large unmetamorphosed and undeformed tonalitic body
of mid-Cretaceous age ( ~112 Ma) that was intruded into sedimentary units
of the Whitehorse Trough in the Stikinia terrane. Geothermobarometric estimates
for eight sites around the pluton indicate that postmagnetization tilting
has been negligible since cooling through the hornblende-crystallization
temperature and that the pluton is a high-level intrusion. Paleomagnetic
measurements for 22 of 24 sites in the pluton yield a well-defined characteristic
remanent magnetization (ChRM) direction that is steeply down and northwards.
The ChRM direction gives a paleopole of 285.5 deg;E, 81.7 deg;N (dp/inf
= 5.3 deg;, infm/inf = 5.7 deg;). When compared with the 112 Ma reference
pole for the North American craton, this paleopole suggests that the northern
Stikinia terrane has been translated northwards by 11.0 +/- 4.8 deg; (1220
+/- 530 km) and rotated clockwise by 59 +/-17 deg. Except for an
estimate from the 70 Ma Carmacks Group volcanics, this translation and
rotation estimate agrees well with previous estimates for units in the
central and southern Intermontane Belt. They suggest
that the terranes of the Intermontane Belt have behaved as a fairly coherent
unit since the Early Cretaceous, moving northward at a minimum average
rate of 2.3 +/- 0.4 cm/a between 140 and 45 Ma.

Gabrielse-H., 1998. Geology of Cry
Lake and Dease Lake map areas, north-central British Columbia. Bulletin-of-the-Geological-Survey-of-Canada.
504, 1-147. Abstract: Cry Lake and Dease Lake
map areas include six well defined terranes each characterized by
distinctive lithological assemblages of different ages, structural styes,
and contained mineral deposits. Miogeoclinal strata
of
Ancestral North America range in age from Late Proterozoic to Early
Mississippian. They have been intruded by voluminous Mesozoic and
Cenozoic granitic rocks, in places associated with tungsten, lead,
and zinc occurrences. The Slide Mountain Terrane
contains Devonian to Permian rocks typical of oceanic and island
are environments. The Kootenay(?) Terrane
is characterized by strongly tectonized, mainly weakly metamorphosed,
siliceous strata. Ultrabasic rocks have potential for jade occurrences
and a few vein deposits of lead, zinc, gold, and silver have been
explored. Rocks assigned to Quesnellia
are of Mesozoic island arc lithologies. In one locality, granodiorite
is host to an important copper deposit. Low grade nickel and chromite
deposits are hosted by an Alaskan-type ultramafic body. The Cache
Creek Terrane is dominantly oceanic in lithology but includes some
assemblages of island arc or rift affinity. The terrane ranges in
age from Devonian through Early Jurassic. Ultrabasic rocks host jade and
asbestos deposits and are spatially related to numerous placer gold deposits.
The island arc or rift volcanics host a large zinc and copper volcanogenic
sulphide deposit. Rocks of Stikinia represent
upper Paleozoic to Lower Jurassic island arc assemblages which are overlain
by upper Mesozoic to Recent sedimentary and volcanic overlap assemblages.
Copper, molybdenum, gold, lead, and zinc occurrences are found in the volcanic
and plutonic rocks. Coal occurs locally in overlap sedimentary rocks.

The following figures illustrate
the relationship between Wrangellia, Stikinia and Quesnellia in the Cascade
region of Washington and British Columbia at the southern end of the Canadian
Cordillera, as interpreted by M.F. McGroder (BGSA, 1991).